I had been banned from the Feminism subreddit for unknown reasons. I have not made any comments that I can see violating the subreddit's rules but I'm banned. I cannot message the mods asking why I was banned as I'm muted for 72 hours. I wish Reddit would enable a function to tell you why you are banned from a particular subreddit.

That's why we won't back down
We won't run and hide
'Cause these are the things we can't deny
I'm passing over you like a satellite
So catch me if I fall
That's why you stick to your game plans and party lives
But at night we're conspiring by candlelight
We are the orphans of the American dreams
Oh shine your light on me

In my experience bans happen for a couple of reasons:
1. Something was taken as a personal attack, particularly when an argument got heated.
2. You violated some rule of conduct or etiquette. (My guess, after looking at the subreddit and your own reddit profile? "- all posts must come from an educated perspective," as you recently made a post like "Feminism is Good but Needs to be More Extreme," which may be well-intentioned but is very vague about what being more extreme means. Maybe someone reacted to that?) That sucks, particularly when there are no warnings, but reddit is big and that subreddit is probably big too.

It happens, particularly at larger sites. I am banned from Jezebel. I still don't know why, but I have a couple of guesses. Those guesses have helped me become a better poster.